Background As life expectancy is increasing and healthy ageing becomes more and more important, skin ageing is a growing topic of interest from both a medical and a commercial point of view. The urgency to unravel the causes of skin ageing is rising. However, there is a lack of objective, simple, noninvasive methods to assess biological skin age - a term introduced to describe how old someone looks, covering both the appearance and function of the skin. A rapid, noninvasive assessment of biological skin age would greatly facilitate the execution of the studies required to find the causes of skin ageing.Objectives To find an objective, easy-to-apply method to assess biological skin age.Methods Skin age score (SAS) was compared with skin auto...